TEST 4: Endocrine Flashcards
Endocrine System overview
(Lecture, p. 662)
-Is a collection of glands that secrete hormones—>
-Hormones are then passed thru the blood to a target organ, where they have cells with receptors that respond to the hormone—>
-That hormone- receptor interaction stimulates a chemical reaction in the target cells—>
-The cellular reaction control metabolism and maintain bodily homeostasis
The 5 main functions of the endocrine system
(P.662)
1.differentiation of the reproductive and CNS in developing fetus
2. Stimulation of sequential growth and development in childhood/ adolescence
3. Coordination of male and female reproductive systems
4. Maintenance of an optimal internal environment throughout life
5. Initiation of corrective and adaptive reprised when emergency demands occur
Functions of the endocrine system
(Lecture, p.662)
Regulates:
-growth and sexual maturation
- energy production and energy utilization by cells (metabolic rate)
-glucose homeostasis
-fluid and electrolyte balance
-circulatory function
Water and lipid soluble hormone characteristics
(Lecture, p. 663)
Water soluble:
-Interact with receptors proteins on the outside of a target cell and cause a cascade of events inside
-Are made from proteins, typically amino acids (soluble in water)
-Available in storage, transient effect
-Half life of seconds to minutes
-Ex = ADH, insulin, epi, growth hormone
Lipid soluble:
-Cross the cell membrane to reach the receptor inside the target cell and interact with the genes inside
-Are Steroid hormones made from cholesterol (soluble in FAT, not water)
-Made on demand (no reserve), persistent effect
-Half life of hours to days
-Ex = estrogen, androgen, steroids
Control of hormones (3 ways)
(Lecture, p. 662)
Negative feedback:
-Most common
-Occurs when an increase level of hormone inhibits further release
-“Hormone stops hormone”
Positive feedback:
-Surges of hormones
-Increased level of hormones stimulates further release
-“Hormone begets hormone”
Cyclic variations:
-Periodic variation in hormone release
-Ex= hormones related to menstruation, cortisol (circadian rhythm)
Mechanism of action for hormones
(Lecture, p. 664)
- Receptors:
-Number is up and down regulated by various stimuli - Intracellular signaling:
-Change membrane permeability, activates intracellular enzymes, and activate genes - Second messenger system:
-Mediates the effect of the hormone on the target cell - Action causing protein synthesis:
-Steroid hormones result in DNA transcription and protein synthesis
Hypothalamic- pituitary axis
(Lecture, p. 667)
-Forms the structural and functional basis for central integration of the neurologic and endocrine systems, creating the neuroendocrine system
Main hormones:
-ACTH
-ADH
-FSH
-LH
-TSH
Pituitary gland
What is it?
Where is it?
Structure?
(Lecture, p.667)
-Part of the hypothalamic- pituitary axis
-Located in Sella turnica (boney cavity at the base of the brain)
-Attached to the base of the brain (hypothalamus) by the pituitary stalk
-Two lobes: anterior and posterior pituitary
Anterior Pituitary hormones (6)
(Lecture, p. 668)
-Aka “adenohypophysis”
-Most pituitary hormones come from the anterior, including:
-Adenocorticotropin (ACTH or corticotropin) : controls secretions of adrenal cortex hormones
-Thyroid stimulating hormone (TSH or Thyrotropin) : controls secretions of thyroxine and triiodothyronine by thyroid gland
-Growth Hormone (GH)
-Prolactin (PRL) : promotes mammary gland development and lactation
-Follicle stimulating hormone (FSH)
-Luteinizing hormone (LH)
Hypothalamic hormones that control anterior pituitary secretion (6)
(Lecture)
-Thyrotropin releasing hormone (TRH)
-Corticotropin releasing hormone (CRH)
-Growth hormone releasing hormone (GHRH)
-Growth hormone inhibitory hormone (GHIH or Somatostatin)
-Gonadotropic releasing hormone (GRH)
-prolactin inhibitory hormone (PIH)
Posterior pituitary 2 main hormones
(Lecture, p. 671)
- Antidiuretic hormone (ADH/ vasopressin): regulated water excretion as urine by the kidneys
- Oxytocin: facilitated milk expression during breast feeding/ role in uterine contraction and labor initiation and progression
Hypothalamic neurons secrete
(Lecture)
-Releasing and inhibitory hormones to regulate production
Growth hormone
What does it do
Mechanisms of action (3)
Metabolic effect
(Lecture, p.671)
-Controls growth of body tissues
3 mechanisms used to grow tissue:
1. Increased mitosis
2. Cell differentiation
3. Cell hypertrophy
Metabolic effects:
increased protein synthesis, increased mobilization of fatty acids from adipose (ketosis), decreased rate of glucose metabolism by cells and decreases glucose utilization (conserves carbs)
Protein building:
enhances amino acid transport, increases transcription of DNA, enhances RNA translation and protein synthesis, decreases the breakdown of proteins and amino acids
Stimulates bone/ cartilage growth:
Increases deposition of protein by chondrocytic and osteogenic cells, increases rate of chondrocyte and osteocyte reproduction, induces conversion of chondrocytes to osteocytes for new bone deposition (cartilage can then convert to bone)
GEM most important role is in children converting cartilage to bone
Thyroid hormone synthesis mechanisms
(Lecture, p.673)
1.Iodides form dietary iodine are pumped from the blood into thyroid gland (TSH regulates the iodide pump activity based on concentration of circulating thyroid hormones)
2. Endoplasmic reticulum synthesizes thyroglobulin protein
3. Thyrotoxine (T4) and triiodothyroxine (T3) form from indication of tyrosine on the thyroglobulin
4. T3 and small amounts of T4 remain bound to thyroglobulin and are stored in gland follicles
5. Thyroid hormones are secreted from the follicles after cleavage from thyroglobulin by proteinases
6. TSH regulates the release of thyroid hormones
Physiologic function of thyroid hormone
(Lecture, p.673)
-Regulates protein, fat, carb metabolism
-Regulates cell metabolic rate
-Regulates body heat production
-Maintains growth hormone secretions and skeletal muscle maturation
-Affects CNS development (fetal-> 2 yo)
-Maintains cardiac rate, force, output
-Maintains secretions of GI tract
-Affects RR and oxygen utilization
*TSH is a negative feedback loop
Quick anatomy/ physiology of pancreas
(Lecture)
Pancreas has 2 types of tissues:
1. Acinar cells: secrete digestive juices
2: islet of Langerhans: secrete insulin, glucagon, somatostatin, and amylin
-Alpha: release amylin
-Beta: release insulin and amylin
-Delta: release somatostatins
-PP: release pancreatic polypeptide
Roles of insulin
(Lecture, p. 675)
Uses:
-Increased glucose uptake into the cells (except the neurons in the brain)
-Increased cell membrane permeability to amino acids, potassium and phosphate ions
-Protein, fat, carbohydrate, nucleic acids synthesis
-Storage of glucose in the liver/ muscle
-Growth and gene expression
ANABOLIC
Control of insulin secretion
(Lecture, p.675)
-Increase in serum glucose= trigger for insulin secretion
-Plasma concentrations of insulin increase rapidly (10-30 could in 3-5 mins) after acute elevation in glucose (eating)
-Then, you get your initial first peak of insulin 5-10 minutes after it’s formed
-Second peak occurs 15 mins later as additional insulin is being made
-Plateau phase in 2-3 hours after eating
-As serum glucose decreases, insulin synthesis/ secretion will taper off
Other controls of insulin
(Lecture)
-Excess serum amino acids (argue, leucine, lysine) promote protein synthesis and cause release of insulin
-Gastrin, secretin, and gastric inhibitory peptide secretion release insulin in anticipation of increased glucose
-Growth hormone, cortisol inhibit insulin
-Parasympathetic nerve activation
Glucagon
(Lecture, p.676)
-Triggered by: decreased glucose, increased amino acid concentration, and exercise
-Opposes the effect of insulin and increase serum glucose concentration
-Stimulates glycogenolysis
-Increases gluconeogensis from amino acids
-Activates adipose lipase to free up fatty acids for conversion to glucose
Non-insulin related implications:
-Increases myocardial contractile
-Increases renal blood flow by dilating afferent arterioles
-Enhances bile secretion
-Inhibits gastric acid secretion
Somatostatin
Effects
Stimulated by
Inhibited by
(Lecture, p. 677)
Somatostatin= Growth hormone inhibiting hormone (GHIH)
-Acts locally on islet cells to decrease production of insulin and glucagon
-Decreases stomach, duodenal, and gallbladder motility
-Decreases excretion of digestive enzymes and absorption by GI tract
-Extends the period of time nutrients and energy enter the blood from digestion
Stimulated by:
-Increased glucose, fatty and amino acids, and the presence of GI hormones in response to food intake
Inhibited by: cholinergics
